To explore the antiviral efficacy, safety and protective ability against mother-to-infant transmission of telbivudine in pregnant patients with chronic hepatitis B (CHB) during the first trimester. Eighty four gravid women who were diagnosed with CHB, in their first trimester of pregnancy, and had refused to terminate their pregnancies were enrolled; all study participants were clinically classified as active hepatitis cases with positivity for both hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg), HBV DNA more than or equal to 107 copies/mL and serum level of alanine aminotarnsferase (ALT) of more than or equal to 4 ULN.Patients with YMDD mutations were excluded from the study. The study participants were divided into a telbivudine treatment group (n=43; administered in the first trimester of pregnancy) and a control group (n=41, consisting of patients who refused to take antivirals). All babies bom to the women in both groups of the study received standard immune prevention (anti-hepatitis B immunoglobulin plus hepatitis B vaccine) and artificial feeding.Data recorded for the women during pregnancy included clinical findings for tests of hepatic and renal function, myocardial enzymes, blood and urine clinical parameters, hepatitis B virus makers and HBV DNA, as well as notation of any adverse reactions. The neonates were evaluated for presence of HBV infection, parameters of growth and development, presence of complications, and Apgar score. At 6 and 12 months old, all infants were evaluated for HBV DNA level and HBsAg presence. The genetic variant rtM204I was detected in one of the women in the treatment group at 36 weeks of pregnancy. One woman in the control group developed severe hepatitis at 28 weeks of pregnancy and was put on the telbivudine treatment The treatment group showed greater recovery rates of ALT than the control group at 12 weeks of pregnancy (62.8% vs.29.3%, P=0.002), 24 weeks of pregnancy (76.7% vs.46.3%, P=0.000), and at ante partum (88.1% vs.60.0%, P=0.004). The treatment group also showed greater HBV DNA-negative conversion rates at 12 weeks of pregnancy (20.9% vs.0, P=0.006), at 24 weeks of pregnancy (37.2% vs.0, P=0.001) and at ante partum (78.6% vs.0, P=0.000), and greater HBeAg seroconversion rates at 12 weeks of pregnancy (2.3% vs.0, P=1.000), at 24 weeks of pregnancy (9.3% vs.0, P=0.116) and at ante partum (2 1.4% vs.0, P=0.002). The HBsAg-positive rates and HBV DNA-positive rates among the infants born to the mothers in the treatment and control groups, respectively, were 2.4% vs.17.5% (P=0.027) at birth, 0 vs.17.5% (P=0.005)at 6 months old and 0 vs.17.5% (P=0.005) at 12 months old. The Apgar scores were not significantly different for the children born to the mothers from the two groups, and all the children showed parameters of growth development within normal limits. Telbivudine administration in the first trimester had a good antiviral curative effect and effectively blocked mother-to-infant transmission in women with CHB. The treatment was safe, causing no obvious adverse reaction in the gravid women or developmental effects on the infants.